The cheapest kilowatt of renewable energy is the kilowatt we save. For that reason, building a clean energy economy isn’t simply about constructing low-carbon plants or implementing a cap-and-trade plan. It’s also about developing an energy grid that more efficiently sends power to homes and businesses — and saves us money along the way.

One of the most promising innovations is a “smart grid,” a system that allows us to combine energy transmission with real-time communication. Author Thomas Friedman calls it the “energy Internet”; it would allow your appliances to detect the cost and source of power from second to second and even sell electricity back to the grid.

A smart grid would help utilities pinpoint the source of outages and turn lights back on faster during a storm. By helping them select the best times to use clean sources, it would also allow them to shrink their carbon footprints. A smart grid would save families hundreds of dollars a year on their power bills, and it would let all of us get by with more output from fewer plants.

Of course, a smart grid is still in the future — but it’s encouraging to know that the American Recovery and Reinvestment Act set aside $4.5 billion to match smart grid investments from utilities, helping them to upgrade home meters, transmission and distribution lines, and communication systems.

Another important way to save energy and money is by investing in the high-tech transmission lines of the future. That’s why I’ve just introduced the Advanced Cable Deployment Authorization Act of 2009, a bill that will help America develop the most advanced transmission technology in the world.

It directs loan guarantee funds in the recovery act toward the expansion of U.S. facilities that make superconducting electrical cable and other efficient wires. I’m also introducing a tax bill that expands the production and distribution of advanced wires that can transmit power over long distances with little loss.

Implementing this new transmission technology will have a number of benefits. For one, we will have a more reliable, secure grid: the latest cables can adjust rapidly and automatically to disruptions, whether weather-related or willful.

Because they’re more efficient than existing cables, they can carry more power in existing rights-of-way. And they have clear environmental benefits: Advanced cables go underground and carry the same amount of power as overhead wires, meaning a dramatically reduced footprint and less land use. In fact, it’s entirely possible that in the not-too-distant future, you’ll be able to drive coast-to-coast without seeing a single power line.

Smart grid systems and advanced cables are just a few of the ways in which we can build a cleaner economy from the ground up. With Congress set to debate important energy legislation this summer, we’re in for a time of dramatic change, with the potential to combat global warming and control our foreign oil addiction. But it’s also crucial to pay attention to the nuts-and-bolts systems that connect energy efficiency to our daily lives, from our appliances to the lines that bring them power. Investments there have the potential to return to us many times over, in the form of higher energy savings and lower bills.